Various magnetic recording media, such as audio tapes, video tapes and computer tapes, are generally subject to gradual wear due to violent sliding contact between a magnetic layer and a magnetic head upon recording or reproduction on a magnetic recording (reproduction) device. Therefore, it is desirable that the magnetic layer should have wear resistance to the sliding contact for a period of time as long as possible, i.e., have high abrasion resistance.
In order to impart high abrasion resistance to a magnetic layer essentially composed of a binder having uniformly dispersed therein a ferromagnetic powder, it has been proposed in Japanese patent application (OPI) No. 29932/85 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") to incorporate into a magnetic layer a nonmagnetic powder having a much higher hardness than the ferromagnetic powder, e.g., Cr.sub.2 O.sub.3, Al.sub.2 O.sub.3 and Sic, and having a particle size of from 0.3 to 0.4 .mu.m as an abrasive. However, such a nonmagnetic powder cannot be dispersed uniformly in a composition for forming a magnetic layer (hereinafter referred to as magnetic composition), but forms a magnetic layer with uneven magnetic characteristics attributed to nonuniformity of the coating composition.
For the purpose of overcoming this problem, addition of a dispersing agent, such as stearic acid, lecithin, higher alcohols having 10 or more carbon atoms, etc., to the composition has been proposed to improve dispersibility of the nonmagnetic powder as described in U.S. Pat. No. 4,719,121, Japanese patent publication No. 48297/87 and Japanese patent application (OPI) No. 214519/87. This technique still fails to achieve sufficient dispersibility as expected, rather resulting in reduction of surface smoothness or electromagnetic conversion characteristics of the magnetic layer.